Selected treatment of fiber blends with resins



United States Patent 3,151,017 SELECTED TREATMENT OF FHBER BLENDS vi EH RESHNS Donald A. Eraiford, Beioit, Wis, assignor to Beloit Corporation, Beloit, Wis, a corporation of Wisconsin No Drawing. Filed .luly 27 1962, Ser. No. 213,913 11 Claims. (til. 162-141) The instant invention relates to the use of paper-treating synthetic resins, and more particularly, to a process of selective treatment of fiber blends with protective and reinforcing resins.

Although it is possible to make a paper web in sheet or molded pulp article form from a dilute fluid stock using only one type of fibres in the stock, it is often found desirable to prepare a stock blend of a plurality of different fibers in order to obtain some particularly desirable re sult in the finally formed product. In addition to having more than one fiber component in the stock, it is also common practice to add one or more non-fibrous particle components in the form of fillers, pigments, etc. such as clays and titanium dioxide.

When the final stock blend of these various fiber components and non-fibrous particle components is finally made up in the beater, it was heretofore conventional practice in many cases to add comparatively small amounts of synthetic resins to the beater, as paper-treating resins, which were used to upgrade the finished web product in wet strength properties and/or dry strength properties. This practice usually involved the addition of the synthetic resin either (a) in a water-soluble form (which often converted to colloidal particles in the dilute concentrations used) or (b) in the form if an emulsion which produced a very finely divided dispersed phase in the stock. In either case it was quite common to effect deppostion of the resin onto the fiber and non-fibrous components in the beater by an adjustment of the pH of the stock blend, and this is ordinarily done by reducing the pH using an acid or using alum. One theory is that the fibers and the non-fibrous particles in the stock blend generally carry a negative charge, and the adjustment of the pH results in the development of cationic characteristics in the discrete resin elements (in colloidal or dispersed form) so that the discrete resin element will discharge on and deposit upon the various fibrous and non-fibrous elements of the stock blend. In any event, the adjustment of the pH apparently does tend to cause the discrete synthetic resin elements to break from solution or suspension and attach to the various fibrous and non-fibrous elements of the original stock blend.

In the case of certain stock blends, however, the foregoing procedure for the use of the so-called paper-treating synthetic resins has not produced consistent results or results commensurate with those expected on the basis of the amount and type of synthetic resin used. Although it is not desired to limit the invention to any particular theory, it is now believed that this procedure of the prior art leaves something to be desired for the reason that the conventional adjustment of the pH results in selective deposition or attachment of the synthetic resin to only one or to less than all of the fibrous and non-fibrous elements present in the original stock blend. This eifect may be explained by virtue of the different natures of the static charges on the various fibrous and non-fibrous elements in the stock blend, since it would seem logical to assume that whatever static charge may be generated on the various discrete synthetic resin elements by the adjustment of the pH would be approximately the same for each of such resin elements. In any event, it would seem that there is a partial or total lack of compatibility between the discrete resin elements and at least some of the fibrous and/ or non-fibrous elements in the dilute stock when the pH is adjusted for the purpose of deposition of the synthetic resin on the stock elements.

The instant invention provides an improved method of forming such a synthetic resin treated stock blend and the resulting fibrous web formed from such stock blend. In general, this is done by initially forming separate dilute stocks for each fibrous and non-fibrous element or component, and treating the fibrous or non-fibrous components in each of these separate stocks with different resins or different resin emulsions so as to assure that a resin or resin emulsion most compatible with the particular fibrous or non-fibrous component is used in each case. In some instances there might be a reasonable amount of similarity between the actual paper-treating resin employed in each of these various stocks, but the differences may involve the emulsion system for the resin and/or the adjustment of the pH and/ or the materials such as alum or acids used to adjust the pH, so that there are actual differences in the resin itself when it is deposited on the suspended fibrous or non-fibrous components in the particular individual stock. For example, the use of alum with a given paper-treating resin may eifect the formation of a cationic aluminum complex with the resin, which complex is the form in which the resin is deposited on a given fibrous component; Whereas the same resin in a different stock may be caused to deposit by adjustment of the pH with an acid which will result in a form of the resin different from the aluminum complex at the time of deposition on the fibers or non-fibrous elements in the particular stock.

It is, therefore, an important object of the instant invention to provide an improved dilute stock blend for use in the formation of fibrous webs, and an improved fibrous Web resulting from the use of such stock blend.

Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed disclosure thereof.

In general, the instant invention consist of a method of forming a dilute stock blend containing at least one fiber component and at least one non-fibrous particle component, which comprises (a) separately forming a dilute stock from each fiber component, and depositing a fiber-treating synthetic resin on the fibers of each such dilute stock; (1)) separately formin a dilute aqueous suspension of each non-fibrous particle component, and depositing a paper-treating synthetic resin on the non-fibrous particles of each such suspension; the resins used in each of the procedures of (a) and (12) being different; and (c) blending together the dilute products of each of the procedures of (a) and (b) to form a stock blend; and the instant invention further relates to the method of producing a fibrous web by forming the aforesaid stock blend on a porous forming surface to deposit the fibrous web on such surface.

It will be appreciated that, once the aforementioned stock blend has been prepared, the fibrous web is produced by forming this stock blend on a porous forming surface such as the conventional forming wire or a porous mold formed of a material such as individual glass beads coated with an epoxy resin to bind the beads together into the desired mold shape. A description of a preferred form of such mold material and the method of making such material is provided in the copending application of Modersohn and Hornbostel entitled Mold, U.S. Serial No. 89,451, filed February 15, 1961. This particular mold material has been found to be quite useful for the formation of generally cylindrical paper articles having a relatively high cylindrical length-to-dia1neter ratio, and the instant invention is particularly useful in connection with the production of molded pulp products of this general type.

In the practice of the instant invention, any of the nuto not more than about 2%.

for a given blend which are not equally or substantially equally compatible with a given paper-treating synthetic resin are first prepared in a separate stock and then treated with a compatible resin (and preferably the resin which has been found to be most compatible under the conditions of deposition used), and each of these separate stocks is then finally blended together to produce the ultimately desired dilute stock blend that is to be used in the formation of the fibrous web product.

In general, the fluid stock blend which is ultimately used in the formation of the fibrous web may be of the general nature and concentration of stock used in conven- :tional paper forming operations. The separate stocks containing individual fibrous or non-fibrous components, however, may be somewhat more concentrated for ease in handling (e.g., having consistencies of perhaps 1% to 5% on a dry fiber basis or dry fibrous or non-fibrous component basis), but it is often more desirable to carry out the deposition of the paper-treating resin using a more dilute stock having a consistency of about 0.01%

In this latter case the resulting stocks may be blended together with little or no additional dilutions so as to obtain a stock blend (preferably having a consistency of about 0.05%) that may be used directly for the formation of the fibrous web in sheet form or in the form of a molded pulp article. (As used herein, the terms percent and mean percent by weight unless otherwise specified.)

Demonstration A A dilute aqueous kraft fiber stock is made up to 1% consistency in a beater and a paper-treating resin emulsion is added to the heater in an amount (of resin solids) equal to 5% of the fiber (on a dry fiber basis). The resin emulsion used is Rhoplex B-lS (which is understood to be a soft acrylic polymer of non-ionic emulsion charge in an aqueous emulsion, and having a pH of 6.06.8 and a viscosity of 50 centipoises, Brookfield, 60 rpm. at 25 C., at pH of 6.3 and an approximate resin .molecular weight of above 2 X After the resin emulsion is thoroughly dispersed in the stock in the beater, alum is added in an amount sufiicient to reduce the pH to 4.5 and the emulsion efiectively breaks to deposit the resin on the stock fibers.

A dilute aqueous cotton linter stock is made up to 1% consistency in a beater and a paper-treating resin emulsion is added to the beater and thoroughly dispersed therein in an amount (of resin solids) equal to 5% of the fiber (on a dry fiber basis). The resin emulsion used is Rhoplex AC-201 (which is understood to be a nonionic emulsion of a hard acrylic polymer, containing 46% solids and having a pH of about 9.0-10.(), and a viscosity of about 100 centipoises, Brookfield, 60 r.p.m. at 25 C., and an approximate resin molecular weight of about 125x10 Alum is then added to the beater in an amount sufiicient to reduce the pH to 4.5 and the emulsion breaks and the resin is deposited on the fibers.

The kraft fiber and cotton linter stocks are then blended together in a beater, in a weight ratio of l to 3, to form a stock blend, to which water is added to reduce the total fiber consistency to 0.05 TAPPI handsheets are formed according to specification T205 M-5 8 (and pressed and dried in an air oven) to obtain sheets having improved dry strength.

The stock blend is also used to form a cylindrical molded pulp article by forcing'the stock blend from the interior through a female glass bead-epoxy bound mold (of the type already described (presenting a cylindrical 4. inner surface to deposit a relatively thick fibrous web layer on the female mold surface. A porous male mold member is optionally then clamped down on the web in the female mold to press the same and hot dry pair is passed through the molds to dry the resulting cylindrical molded pulp article having superior dry strength. In contrast, a male mold member of this same structure may be introduced into the blend with a vacuum drawn on the interior of the mold to form the fibrous web layer on the outer forming surface thereof, and such fibrous web may be partially dried (after the mold and web are removed from the stock blend), and this fibrous web (or molded pulp article) may then be removed from the male mold and placed in a hot air oven to complete the drying thereof.

Clay fillers and pigments may also be incorporated in the stock blend. For example, an amount of clay equal to about 20% of the total dry fiber content of the blend and/or an amount of titanium dioxide equal to about 3% of the total dry fiber content of the blend may be added to the blend in the beater, with or with prior treatment with a resin. Resin treatment in the case of each of these materials is effected by first making up a separate suspension or stock having about 1% consistency and then adding the resin in an amount (of resin solids) equal to about 10% of the solids content of the stock. The resin used is Rhoplex B60A (which is understood to be a low viscosity non-ionic aqueous emulsion of a soft acrylic resin, and having a pH of 9.0 to 9.8, a viscosity range of 25 centipoises at 6.7 pH to 320 centipoises at 9.6 pH, Brookfield, 60 rpm. at 25 C., 46.5% solids and an approximate resin molecular weight of x10 Alum is then added in an amount sufficient to reduce the pH to 4.5 and the emulsion breaks to deposit the resin on the clay and/or titanium dioxide particles in the stock, which is then added to the stock fiber blend in the beater, prior to or during the adjustment to the desired consistency of 0.05%.

Demonstration B Demonstration C A procedure is carried out that is the same as that described in Demonstration B, except that the cotton linters are acetylated first to produce cellulose acetate fibers prior to the formation of the dilute aqueous stock made up to 1% consistency in the heater, and it is found that there is a distinct improvement in wet and dry strength in the resulting fibrous web products (particularly as compared to a corresponding product wherein the cellulose acetate fibers are not treated separately with a papertreating resin or elastomer).

The procedure of the foregoing paragraph is repeated, except that the cellulose acetate fibers are replaced by cellulose ether fibers, and the corresponding irnprovement is obtained.

The procedure of the previous paragraphs is reputed, except that the cotton linters are nitrated prior to the formation of the dilute aqueous stock of 1% consistency in the beater, so that cellulose nitrate fibers are employed in the stock formulation, and a corresponding improvement is obtained in the resulting fibrous web products.

Ordinarily the cellulose ester and ether fibers per se will not form a particularly strong paper when formed from an aqueous stock system, but the effect of depositing a neoprene coating onto these fibers materially assists the bonding of these fibers with the resin-treated kraft fibers adding sodium hydroxide.

in the ultimate formation of a substantially stronger fibrous web.

Demonstration D The procedure of Demonstration A is carried out, eX- cept that the resin emulsion used to treat the cotton linters in the initial preparation of cotton linter stock is replaced by a latex of butadiene-acrylonitrile (equimolar) copolymer, wherein the solid elastomeric content is equal to about 2% of the dry weight of the cotton linters, and the resulting fibrous web products are found to have superior strength.

Comparable results are obtained using a latex of a butadiene-styrene (equimolar) copolymer or a butadienevinyl chloride (3 to 1 molar ratio) compolymer.

Demonstration E Still another procedure may be employed that is the same as that of Demonstration A, except that a neoprene latex is used to treat the cotton linters. The neoprene latex used contains 5% formaldehyde naphthalene sodium sulfonate as a dispersing agent and is diluted to 5% solids. In this procedure, parts of zinc oxide and 3 parts of a conventional antioxidant (e.g., guanadine) for each 100 parts of neoprene in the latex being used are first added to the beater containing a dilute aqueous cotton linter stock having a consistency of about 1%. About 4 parts of ammonium kaceinate in a dulte aqueous solution are also added, and the stock is adjusted to a pH of 8.5 by The neoprene latex is then added in an amount equal to approximately 2% on a dry fiber basis and after the latex is dispersed in the stock, alum is added to reduce the pH to 4.5 which effectively breaks the emulsion and deposits the neoprene on the cotton linters. The fibrous Webs resulting from this procedure are found to have improved strength properties.

Demonstration F The invention may also be demonstrated using various different pulps with the conventional melamine-formaldehyde resins or the anionic or cationic urea formaldehyde paper-treating resins.

A melamine-formaldehyde paper-treating resin is prepared by dissolving in 100 parts of water a commercially available trimethylol melamine powder in an amount equivalent to about 10 parts by weight and an amount of hydrochloric acid equal to 0.8 mol for each mol of trimethylol melamine, and allowing the solution to age. The resin condenses into particles within the colloidal range 1 (about 10 to monomer units), as indicated by the appearance of a blue haze in the dispersion within several hours. The resulting colloidal resin particles have a molecular weight within the range of about 1700 to 4000 and function as cations in an aqueous system. The aqueous system of melamine-formaldehyde colloidal particles may be added directly to the stock with adequate circulation, but without the necessity of processing the stock through violent agitation in the beater, and the colloidal particles are attracted by the generally negatively charged paper fiber in dilute aqueous suspension.

An anionic type urea'forrnaldehyde paper-treating resin is prepared by heating for about one hour a 20% (solids) aqueous solution of 1 mol of urea, 2 mole of formaldehyde, 0.1 mol of sodium bisulfite, and an amount of ammonium hydroxide suflicient to adjust the pH to 6. This results in what is known as a sulfomethylated ureaformaldehyde resin which is an anionic type resin, which is ordinarily diluted to about 1 to 5% with water at about C. In order to deposit this anionic type resin onto the paper fibers in dilute aqueous suspension, the pH is adjusted to 4.0 to 4.5 by the addition of alum; and the resin is preferably added to the stock after violent agitation of the stock has been completed, but it is added with a sufficient amount of agitation to effect complete dispersion of the resin throughout the stock.

Cationic type urea-formaldehyde resins are also used in the practice of the instant invention, and the cationic urea-formaldehyde resin employed hereinafter is prepared by formation of a B-stage urea-formaldehyde resin by reacting in a 20% (solids) aqueous solution 11 parts of urea, 35 parts of formalin, and 1 part of dicyandiamidine formats. In this system the cationic resin is formed and the resin is merely added to the stock (again preferably after violent agitation in the beater) with sufficient agitation to disperse the same throughout t stock, and the cationic resinous particles or colloids deposit on the fibers. if desired, adjustments in the pH with alum may be carried out, but the cationic resins will deposit over a range of pH values from 4.0 to 6.5.

In the subsequent demonstrations, the amount of melamine-formaldehyde, anionic urea-formaldehyde and cationic urea-formaldehyde resins deposited on the fibers is, in each case, 3 on a dry fiber basis.

(1) in the formation of fibrous pulp articles in accordance with the forming procedure set forth in Demonstration A, from equal parts by weight of alpha cellulose and bleached ltraft, the alpha cellulose is first prepared in a dilute aqueous stock of 1% consistency and then treated with the aforementioned melamine-formaldehyde paper-treating resin; and the bleached lzraft is first prepared in a separate dilute aqueous stock of 1% consistency and treated with the aforementioned cationic urea-formaldehyde paper-treating resin. The two stocks are then combined with moderate agitation to effect complete intermingling of the fibers, and the resulting stock blend is forced against a forming surface to obtain a formed pulp article, which is dried in a hot air oven, and the resulting paper product was found to have superior dry tensile strength and improved wet tensile strength.

(2) A fibrous pulp article is made from a combination of equal parts of alpha cellulose, bleached kraft and unbleached kraft, by carrying out separate resin paper treatment of the alpha cellulose and bleached kraft fibers in the manner described in previous paragraph (1). In addition, the unbleached kraft fibers are made up in a dilute aqueous stock of about 1% consistency and treated with the aforementioned anionic urea-formaldehyde paper-treating resin. The three dilute stocks are then blended together and diluted to a consistency of about 0.5% (which is the consistency used in the previous paragraph for wet formation) and then the stock blend is forced against a forming surface in the manner hereinbefore described to obtain a fibrous web which is dried in a hot air oven (to complete the condensation of the various paper-treating resins) so as to obtain a fibrous Web of superior dry and wet tensile strength.

(3) Comparable results are obtained by treating a 1% consistency unbleached sulfite pulp stock with the melamine formaldehyde paper-treating resin, and treating a bleached sulfite pulp stock of 1% consistency with the aforementioned cationic urea-formaldehyde paper-treating resin; and then combining the stocks to form a blend and forcing the blend against a forming surface to effect the formation of a molded pulp article, which is dried in a hot air oven to complete the condensation of the resins, so as to obtain a paper having superior dry and et tensile strength. In this particular combination of fibers the stocks are blended to give a weight ratio of 2 to 1 for the bleached sulfite fibers to the unbleached sulfite fibers.

It will thus be seen that the instant invention may be carried out by selectively treating stocks containing any one or any one type of a plurality of different fibrous and non-fibrous materials, which include the conventional fillers and pigments, as well as any of the conventional fibrous materials which include rag pulp, alpha cellulose pulp, bleached kraft pulp, unbleached lcraft pulp, unbleached ground Wood pulp, unbleached semi-chemical pulp, bleached sulfite pulp, unbleached sulfite pulp, cotton lint-ers (in natural fiber condition and/or in etherified or esterified condition), etc. in addition, the resins deposited on the individual fibers or fiber types in each separate stock may be any one of the conventional resins used as beater and wet end additives and/ or wet strength resins, which include water-soluble resins and/or emulsions of comparatively water insoluble resins, which include phenol formaldehyde resins, the various acrylic resins such as the polyacrylamides and copolymers thereof with acrylic acid, and/or acrylic acid esters or salts, latices of the well known elastomeric polymers such as copolymers of butadiene with styrene, acrylonitrile and/ or vinyl chloride, the resinous water-soluble cellulose derivatives such as carboxy methyl cellulose, hydroxy ethyl cellulose, and methyl cellulose, and melamineformaldehyde paper-treating resins, anionic urea-formaldehyde paper-treating resins and cationic urea-formaldehyde paper-treating resins. in each case, the resin employed is selected for its compatibility with the particular fibers or fiber-type which will be selectively treated in a dilute stock, and the several dilute stocks thus prepared are finally blended together to form the final stock blend which is used in the fibrous web formation.

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.

I claim as my invention:

1; A method of producing a stock blend of a plurality of different fibers, which comprises separately forming a different dilute aqueous stock for each of such different fibers, depositing a fiber-treating synthetic resin on the fibers in each of said different stocks using in each case a resin compatible with the fibers but different from the resin used in any other of said different stocks, and then blending the different stocks together, the resin deposition procedure used herein to deposit a resin on the fibers of a given stock in accordance with the claimed method being a procedure selectively preferential for deposition of such resin on such fibers to such an extent that carrying out of an otherwise identical procedure except that some of the aforesaid different fibers are also present in the stock with such fibers would give an unfavorable result as a consequence of lack of uniform preference of such resin for all of the fibers then present.

2. A method of producing a fibrous web formed of a plurality of different fibers, which comprises separately forming a different dilute aqueous stock for each of such different fibers, depositing a fiber-treating synthetic resin on the fibers in each of said different stocks using in each case a resin compatible with the fibers but different from the resin used in any other of said different stocks, then blending the different stocks together, and then forcing the stock blend through a porous forming surface to deposit a fibrous Web on such surface, the resin deposition procedure used herein to deposit a resin on the fibers of a given stock in accordance with the claimed method being a procedure selectively preferential for deposition of such resin on such fibers to such an extent that carrying out of an otherwise identical procedure except that some of the aforesaid different fibers are also present in the stock with such fibers would give an unfavorable result as a consequence of lack of uniform preference of such resin for all of the fibers then present.

3. A method of producing a stock blend of a plurality of different fibers, which comprises separately forming a different dilute aqueous stock for each of such different fibers, introducing into each of said different stocks a fiber-treating resin emulsion using in each case a resin emulsion which will deposit a compatible resin onto the fibers in such stock but which is a resin emulsion different from that used in any other of said different stocks, and then blending the different stocks together, the resin deposition procedure used herein to deposit a resin on the fibers of a given stock in accordance with the claimed method being a procedure selectively preferential for deposition of such resin on such fibers to such an extent that carrying out of an otherwise identical procedure exf2? cept that some of the aforesaid different fibers are also present in the stock with such fibers would give an unfavorable result as a consequence of lack of uniform preference of such resin for all of the fibers then present.

4. A method of producing a fibrous web formed of a plurality of different fibers, which comprises separately forming a different dilute aqueous stock for each of such different fibers, introducing into each of said different stocks a fiber-treating resin emulsion using in each case a resin emulsion which will deposit a compatible resin onto the fibers in such stock but which is a resin emulsion different from that used in any other of said different stocks, then blending the different stocks together, and then forcing the stock blend through a porous forming surface to deposit a fibrous web on such surface, the resin deposition procedure used herein to deposit a resin on the fibers of a given stock in accordance with the claimed method being a procedure selectively preferential for deposition of such resin on such fibers to such an extent that carrying out of an otherwise identical procedure except that some of the aforesaid different fibers are also present in the stock with such fibers would give an unfavorable result as a consequence of lack of uniform preference of such resin for all of the fibers then present.

5. A method of forming a dilute stock blend of cotton linters and kraft pulp which comprises (a) separately forming a first dilute aqueous stock from kraft pulp, and

depositing a first fiber-treating synthetic resin on the kraft pulp fibers in said first stock;

(b) separately forming a second dilute aqueous stock from cotton linters, and

depositing a second fiber-treating synthetic resin on the cotton linters in said second stock, said second resin being different from said first resin and each of said resins being compatible with the fibers upon which it is deposited;

and (c) then blending the first and second stocks together;

the resin deposition procedure used in step (b) herein to deposit a resin on the cotton linters in the second stock in accordance with the claimed method being a procedure selectively preferential for deposition of such resin on such cotton linters to such an extent that carrying out of an otherwise identical procedure except that some of the aforesaid kraft pulp fibers are also present in the aforesaid second stock with such cotton linters would give an unfavorable result as a consequence of lack of uniform preference of such resin for both the kraft pulp fibers and the cotton linters then present.

6. A method of producing a fibrous web formed of cotton linters and kraft pulp which comprises (a) separately forming a first dilute aqueous stock from kraft pulp, and

depositing a first fiber-treating synthetic resin on the kraft pulp fibers in said first stock;

(11) separately forming a second dilute aqueous stock from cotton linters, and

depositing a second fiber-treating synthetic resin on the cotton linters in said second stock, said second resin being different from said first resin and each of said resins being compatible with the fibers upon which it is deposited;

(c) then blending the first and second stocks together;

and

(d) then forcing the stock blend through a porous forming surface to deposit a fibrous web on such surface; the resin deposition procedure used in step (b) herein to deposit a resin on the cotton linters in the second stock in accordance with the claimed method being a procedure selectively preferential for deposition of such resin on such cotton linters to such an extent that carrying out of an otherwise identical procedure except that some of the aforesaid kraft pulp fibers are also present in the aforesaid second stock with such cotton linters would give an unfavorable result as a consequence of lack of uniform preference of such resin for both the kraft pulp fibers and the cotton linters then present.

7. A method of forming a dilute stock blend containing a plurality of different fiber components and at least one non-fibrous particle component, which comprises (a) separately forming a dilute stock from each fiber component, and

depositing a fiber-treating synthetic resin on the fibers of each such dilute stock;

(b) separately forming a dilute aqueous suspension of each non-fibrous particle component, and

depositing a paper-treating synthetic resin on the non-fibrous particles of each such suspension; the resins used in each of the procedures of (a) and (b) being different;

and (c) blending together the dilute products of each of the procedures of (a) and (b) to form .a stock blend; the resin deposition procedure used in step (a) herein to deposit a resin on the fibers of a given stock in accordance with the claimed method being a procedure selectively preferential for deposition of such resin on such fibers to such an extent that carrying out of an otherwise identical procedure except that some of the fibers of an aforesaid different fiber component are also present in the stock with such fibers would give an unfavorable result as a consequence of a lack of uniform preference of such resin for all of the fibers then present.

8. A method of producing a fibrous web containing a plurality of different fiber components and at least one non-fibrous particle component, which comprises (a) separately forming a dilute stock from each fiber component, and

depositing a fiber-treating synthetic resin on the fibers of each such dilute stock;

(b) separately forming a dilute aqueous suspension of each non-fibrous particle component, and

depositing a paper-treating synthetic resin on the non-fibrous particles of each such suspension; the resins used in each of the procedures of (a) and (b) being different; (1:) blending together the dilute products of each of the procedures of (a) and (b) to form a stock blend;

and

(d) then forcing the stock blend through a porous forming surface to deposit the fibrous web on such surface; the resin deposition procedure used in step ([1) herein to deposit a resin on the fibers of a given dilute stock in accordance with the claimed method being a procedure selectively preferential for the deposition of such resin on such fibers to such an extent that carrying out of an otherwise identical procedure except that some of the aforesaid nonfibrous particles are also present in the stock with such fibers would give an unfavorable result as a consequence of lack of uniform preference of such resin for both such fibers and such particles.

9. A method of forming a dilute stock blend containing a plurality of different fiber components and at least one non-fibrous particle component, which comprises (a) separately forming a dilute stock from each fiber component, and

depositing a different fiber-treating synthetic resin on the fibers of each such dilute stock;

(b) separately forming a dilute aqueous suspension of each nonefibrous particle component, and

(c) blending together the dilute products of each of the procedures of (a) and (b) to form a stock blend; the resin deposition procedure used in step (a) herein to deposit a resin on the fibers of a given dilute stock in accordance with the claimed. method being a procedure selectively preferential for the deposition of such resin on such fibers to such an extent that carrying out of an otherwise identical procedure except that some of the aforesaid non-fibrous particles are also present in the stock with such fibers would give an unfavorable result as a consequence of lack of uniform preference of such resin for both such fibers and such particles.

10. A method of producing a fibrous web containing a plurality of different fiber components and at least one non-fibrous particle component, which comprises (a) separately forming a dilute stock from each fiber component, and

depositing a different fiber-treating synthetic resin on the fibers of each such dilute stock;

(b) separately forming a dilute aqueous suspension of each non-fibrous particle component, and

(c) blending together the dilute products of each of the procedures of (a) and (b) to form a stock blend;

and

(d) then forcing the stock blend through a porous forming surface to deposit the fibrous web on such surface; the resin deposition procedure used in step (a) herein to deposit a resin on the fibers of a given dilute stock in accordance with the claimed method being a procedure selectively preferential for the deposition of such resin on such fibers to such an extent that carrying out of an otherwise identical procedure except that some of the aforesaid non-fibrous particles are also present in the stock with such fibers would give an unfavorable result as a consequence of lack of uniform preference of such resin for both such fibers and such particles.

11. A method of forming a dilute stock containing a fiber component and a non-fibrous particle component, which comprises the steps of g (a) separately forming a dilute aqueous stock from the fiber component, and depositing a first resin on the fibers thereof;

(b) separately forming a dilute aqueous suspension of such non-fibrous particle component, and depositing a second resin different from the first resin on the particles in such suspension; and

(c) then blending together the separately resin-treated products of steps (a) and (b) to form a final dilute stock; the second resin deposition procedure of step (b) being selective for deposition of such second resin on such particles to such an extent that carrying out of an otherwise identical procedure except that fibers described in step (a) are also present in the dilute aqueous particle suspension would result in lack of uniform preference of the second resin for both the particle and fiber components present such that defective resin deposition on one of the components is obtained.

References Cited in the file of this patent UNITED STATES PATENTS 2,027,090 Carter Jan. 7, 1936 2,332,226 Hutchins Oct. 19, 1943 2,694,630 Landes Nov. 16, 1954 2,859,109 Hawley Nov. 4, 1958 3,057,772 Magill Oct. 9, 1962 

1. A METHOD OF PRODUCING A STOCK BLEND OF A PLURALITY OF DIFFERENT FIBERS, WHICH COMPRISES SEPARATELY FORMING A DIFFERENT DILUTE AQUEOUS STOCK FOR EACH OF SUCH DIFFERENT FIBERS, DEPOSITING A FIBER-TREATING SYNTHETIC RESIN ON THE FIBERS IN EACH OF SAID DIFFERENT STOCKS USING IN EACH CASE A RESIN COMPATIBLE WITH THE FIBERS BUT DIFFERENT FROM THE RESIN USED IN ANY OTHER OF SAID DIFFERENT STOCKS, AND THEN BLENDING THE DIFFERENT STOCKS TOGETHER, THE RESIN DEPOSITION PROCEDURE USED HEREIN TO DEPOSIT A RESIN ON THE FIBERS OF A GIVEN STOCK IN ACCORDANCE WITH THE CLAIMED METHOD BEING A PROCEDURE SELECTIVELY PREFERENTIAL FOR DEPOSITION OF SUCH RESIN ON SUCH FIBERS TO SUCH AN EXTENT THAT CARRYING OUT OF AN OTHERWISE IDENTICAL PROCEDURE EXCEPT THAT SOME OF TH AFORESAID DIFFERENT FIBERS ARE ALSO PRESENT IN THE STOCK WITH SUCH FIBERS WOULD GIVE AN UNFAVORABLE RESULT AS A CONSEQUENCE OF LACK OF UNIFORM PREFERENCE OF SUCH RESIN FOR ALL OF THE FIBERS THEN PRESENT. 